12044( 4) - 17-Nov-2009 15:56:29 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12044 Version: 4 Check-in Time: 17-Nov-2009 15:56:29 STScI Edit Number: 2 Title DD Observations of the Coldest Brown Dwarf ------------------------------------------------------------------------------------ Type Cycle GO/DD 17 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Peter Eisenhardt Jet Propulsion Laboratory CoI: Dr. Daniel Stern Jet Propulsion Laboratory N CoI: Dr. Amanda K. Mainzer Jet Propulsion Laboratory N CoI: Prof. Edward L. Wright University of California - Los Angeles N CoI: Mr. Roger Griffith Jet Propulsion Laboratory N CoI: Dr. Matthew L. N. Ashby Smithsonian Institution Astrophysical N Observatory CoI: Dr. Mark Brodwin Smithsonian Institution Astrophysical N Observatory CoI: Dr. Michael J.I. Brown Monash University N CoI: Mr. Shane Bussmann University of Arizona N CoI: Dr. Arjun Dey National Optical Astronomy Observatories, N AURA CoI: Dr. Andrea M. Ghez University of California - Los Angeles N CoI: Dr. Eilat Glikman Yale University N CoI: Dr. Anthony H. Gonzalez University of Florida N CoI: Dr. J. Davy Kirkpatrick California Institute of Technology N CoI: Dr. Quinn Konopacky University of California - Los Angeles N CoI: Mr. David Vollbach University of Florida N CoI: Dr. Shelley A. Wright University of California - Berkeley N ------------------------------------------------------------------------------------ Abstract We request DD observations of the SDWFS J1433+35, which is a strong candidate for the coldest brown dwarf yet discovered and the first example of the elusive "Y-dwarf" spectral class. This source was discovered from a deep, wide-field survey of 10 square degrees with the IRAC instrument on Spitzer, and is redder in both [3.6]-[4.5] and H-[4.5] than any published brown dwarfs. The spectrum falls beyond 5 microns, strongly implying that the red mid-infrared colors are due to methane absorption in the IRAC 3.6 micron channel rather than dust obscuration. The source is undetected in deep, ground-based near-IR images, with a H>24.2 (Vega) limit derived from Keck AO imaging. The proposed WFC3 imaging should provide detections in two near-infrared bands. By showing the target is morphologically unresolved and that it has the non-uniform spectral energy distribution of an ultracool brown dwarf, the proposed observations will definitely show that (i) SDWFS J1433+35 is the coldest brown dwarf known, (ii) test models of ultracool, planet-like, brown dwarf atmospheres, and (iii) refine predictions and strategies for the Wide-Field Infrared Survey Explorer (WISE; planned to launch this December). ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose multi-band near-IR imaging observations of SDWFS 12044( 4) - 17-Nov-2009 15:56:29 - [ 2] J143356.62+351849.2, the Y-dwarf candidate, with WFC3. Such data will confirm the nature of this source (i) by showing that it is unresolved (as expected for a brown dwarf, but not for a dusty galaxy, the most likely --- but still unlikely --- alternate explanation for the unusual SED), and (ii) by showing that the near-IR portion of the SED has the characteristic and distinguishing SED of an ultracool brown dwarf. Given the faintness of the target, these observations are beyond the capabilities of ground-based observatories, but well within the reach of a modestly sized (7 orbit) HST program. We have used the WFC3 exposure time calculator to estimate the time needed under default background and detection assumptions to detect a 400 K Burrows et al. (2003) non-equilibrium brown dwarf model, normalized to H=26. This is an order of magnitude deeper than our Keck AO derived limit (Figure~3). We investigated models with temperatures ranging from 400 to 600 K assuming both equilibrium or non-equilibrium conditions, and the 400 K non-equilibrium model was found to be the most conservative (e.g., the most challenging) case. The most sensitive filter for this model is F140W. To achieve a signal-to-noise (SNR) of 5 in F140W will require 1.9 hours of exposure time and should provide adequate sensitivity to determine whether the source is morphologically unresolved. Assuming 40 usable minutes of integration per orbit, this is achievable in 3 orbits. To further distinguish between the Y-dwarf and DOG hypotheses, we request 2.6 hours (4 orbits) with F127M which will achieve SNR of 5 for the brown dwarf spectrum, but substantially less on a DOG, since the brown dwarf spectra peak up in F127M. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12044( 4) - 17-Nov-2009 15:56:29 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SDWFSJ143356 STAR, BROWN DWARF RA=14H33M56.6200S +/- 0.5", J2000 V = 35. +/- 5 J>21.9, H>24.2, Ks>18.8, .62+351849.2 DEC=+35D18'49.20" +/- 0.5" [3.6]=20.71, [4.5]=18.47 Reference Frame: ICRS Comments: ------------------------------------------------------------------------------------------------------------------------------------ 12044( 4) - 17-Nov-2009 15:56:29 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 5.725 Line_Spacing 3.655 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 12044( 4) - 17-Nov-2009 15:56:29 - [ 5] Visit: 01 Visit Requirements: BEFORE 01-JAN-2010:00:00:00 On Hold Comments: Additional Comments: F140W imaging Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDWFSJ14335 WFC3/IR MULTIAC IR F140W SAMP-SEQ=SPARS50, NSAMP=15 1 DEF GS ACQ SCENARIO SINGLE; 6.62+351849 CUM PATTERN 1 1 .2 ------------------------------------------------------------------------------------------------------------------------------------ 2 SDWFSJ14335 WFC3/IR MULTIAC IR F140W SAMP-SEQ=SPARS50, NSAMP=15 1 DEF POS TARG 1., 1.; PATTERN 6.62+351849 CUM 1 2 .2 ------------------------------------------------------------------------------------------------------------------------------------ 3 SDWFSJ14335 WFC3/IR MULTIAC IR F140W SAMP-SEQ=SPARS50, NSAMP=15 1 DEF POS TARG -1., -1.; 6.62+351849 CUM PATTERN 1 3 .2 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F140W 1 none none none 1 N/A 849.2 CUM SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F140W 2 none none none 1 N/A 849.2 CUM SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F140W 3 none none none 1 N/A 849.2 CUM SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F140W 4 none none none 1 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F140W 1 none none none 2 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F140W 2 none none none 2 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F140W 3 none none none 2 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F140W 4 none none none 2 N/A 849.2 CUM SDWFSJ143356.62+351 3 WFC3/IR MULTIAC IR F140W 1 none none none 3 N/A 849.2 CUM SDWFSJ143356.62+351 3 WFC3/IR MULTIAC IR F140W 2 none none none 3 N/A 849.2 CUM SDWFSJ143356.62+351 3 WFC3/IR MULTIAC IR F140W 3 none none none 3 N/A 849.2 CUM SDWFSJ143356.62+351 3 WFC3/IR MULTIAC IR F140W 4 none none none 3 N/A 849.2 CUM 12044( 4) - 17-Nov-2009 15:56:29 - [ 6] Visit: 02 Visit Requirements: BEFORE 01-JAN-2010:00:00:00 On Hold Comments: Additional Comments: F127M imaging Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDWFSJ14335 WFC3/IR MULTIAC IR F127M SAMP-SEQ=SPARS100, NSAMP=15 1 DEF GS ACQ SCENARIO SINGLE; 6.62+351849 CUM PATTERN 1 1 .2 ------------------------------------------------------------------------------------------------------------------------------------ 2 SDWFSJ14335 WFC3/IR MULTIAC IR F127M SAMP-SEQ=SPARS100, NSAMP=15 1 DEF POS TARG 1., 1.; PATTERN 6.62+351849 CUM 1 2 .2 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F127M 1 none none none 1 N/A 849.2 CUM SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F127M 2 none none none 1 N/A 849.2 CUM SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F127M 3 none none none 2 N/A 849.2 CUM SDWFSJ143356.62+351 1 WFC3/IR MULTIAC IR F127M 4 none none none 2 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F127M 1 none none none 3 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F127M 2 none none none 3 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F127M 3 none none none 4 N/A 849.2 CUM SDWFSJ143356.62+351 2 WFC3/IR MULTIAC IR F127M 4 none none none 4 N/A 849.2 CUM 12044( 4) - 17-Nov-2009 15:56:29 - [ 7] Summary Form for Proposal 12044 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=15, SAMP-SEQ=SPARS100, SAMP-SEQ=SPARS50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 01-JAN-2010:00:00:00, GS ACQ SCENARIO SINGLE, PATTERN 1 1, PATTERN 1 2, PATTERN 1 3, POS TARG -1., -1., POS TARG 1., 1. ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F127M, F140W ------------------------------------------------------------------------------------------------------------------------------------ Target Names SDWFSJ143356.62+351849.2 ------------------------------------------------------------------------------------------------------------------------------------